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L. Hanzo, P. Cherriman
Department of Electronics and Computer Science,
University of Southampton, SO17 1BJ, UK.
Tel: +44 703 593125, Fax: +44 703 593045
Email:
lh@ecs.soton.ac.uk
© 1998 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to refuse any copyrighted component of this work in other works must be obtained from the IEEE.
Submitted to proceedings of IEEE, 1998
Second generation mobile radio standards have not been designed with video communications in mind, although the employment of error-resilient, constant rate video codecs over these systems is realistic. The imminent next generation will be able to support higher rates and better communications integrity in support of video applications. The geographic variation of the wireless channel capacity across propagation cells suggests that substantial performance gains are promised by intelligent multimode transceivers. These transceivers require, however, a programable-rate video codec, such as the H.263 scheme, which is inherently error sensitive. This deficiency is mitigated in our candidate system by an adaptive packetisation and packet acknowledgement scheme, which superimposes the corresponding strongly protected binary flag on to the reverse-link messages of a Time Division Duplex (TDD) scheme, instructing both reconstruction frame buffers to drop corrupted packets and refrain from updating the corresponding video frame sections. This measure does not require high-latency, high-delay Automatic Repeat Request (ARQ) techniques, yet tolerating high packet dropping rates. When using power control, the video quality is a direct function of the packet error rate maintained. However, by improving the system's power budget at the cost of an increased power consumption it is possible to maintain an increased channel SNR, which in turn supports the employment of higher order modem modes, while maintaining the required target packet error rate. A higher-order constellation then ultimately facilitates the transmission of higher quality video at an increased bitrate.